Drafting instrument



MarchZl, 1950 r w. H. HOWARD 2,501,521

' DRAFTING INSTRUMENT Filed Sept. 23, 1946 x 92351111119 V- n 4 Inventor8 7. 2' (l/(LIAM ll. you/Amp FIEFE Patented Mar. 21, 1950 UNITED STATESPATENT OFFICE DRAFTING INSTRUMENT William H. Howard, Niagara Falls,Ontario,

Canada Application September 23, 1946, Serial No. 698,722

4 Claims.

This invention relates to new and useful improvements and structuralrefinements in draft- Another object of the invention is to provide a adrafting instrument which may be readily adapted for use in associationwith drafting machines.

1 An additional object of the invention is to provide a draftinginstrument which is simple in construction and operation, and which willnot easily become damaged.

With the above more important objects in view, and such other objects asmay become apparent as this specification proceeds, the inventionoonsists essentially of the arrangement and construction of parts asillustrated in the accompanying drawings, in which:

Figure 1 is a top plan view of the invention, and

Figure 2 is a cross sectional view taken substantially in the plane ofthe line 2-2 in Figure 1.

Referring now to the accompanying drawings in detail, the inventionconsists of a drafting instrument designated generally by the referencecharacter 5, the same embodying in its construction a pair of plates 6and I, each formed from plates having the general configuration of aright-angled isosceles triangle.

The basal! opposite the right-angled apex 9 of the plate 6 is formedwith a semi-circular recess II having a center at point Ill, while theright-angled apex portion of the plate from which plate I is made isrelieved as at l2, the relieved portion of the plate being of asector-like formation.

A transparent circular protractor I3 is posi tioned between the plates 6and I, and it will be noted that the arcuate edges I 4 and I5 of the twoplates respectively, are complementary to the circumferential edge ofthe protractor. It will be also observed that the protractor Is as wellas the plates 6 and I are disposed in a common plane.

The plate 6 is provided with a substantially 55 T-shaped bearing bracketI6 formed of translucent material, while the plate I is equipped with asuperimposed translucent bracket I'I. These brackets are secured to therespective plates by means of rivets i8, and the bracket I 6 is offsetas at I9 to provide a space for a portion of the bracket I I, as is bestshown in Figure 2.

A pivot pin 20 is secured in the center of the protractor I3 and alsoengages both the bracket I6 and the bracket I'I. In this manner, theplates 6 and I are pivotally connected to the protractor I3, so that thecenter I D is coincident with the right-angled apex of the plate fromwhich plate I is made and with the center of the protractor I3.

Means are provided for releasably locking the plates 6 and 1 ina-predetermined position with respect to the protractor I3, the sameassuming the form of a screw 22 associated with each of the said plates.For the purpose of accommodating the screw head, each of said plates isprovided adjacent the arcuate edge (M or I 5) thereof with asubstantially semi-circular recess 23, while the protractor I3 is formedadjacent its circumferential edge with a marginal undercut 24. Thescrews 22 extend through the brackets I6 and I1, and carry suitableknurled adjusting nuts 25. v

The protractor I3 is equipped, on the underside thereof, with a suitablygraduated scale 26, and the underside of each of the plates 6 and] isinscribed with an index line 21. It should be also noted that one-halfthe length of the base 8 is equal to each of the two equal sides 28 oftract complemental and supplemental angles, as

has been the conventional practice in determining angular relationships.

It is believed that the application and use of the invention, as well asthe advantages resulting therefrom, will be readily apparent to thoseskilled in the art and accordingly, further description thereof at thispoint is considered unnecessary.

Whil in the foregoing there has been shown and described the preferredembodiment of this invention it is to be understood that minor changesin the details of construction, combination and arrangement of parts maybe resorted to without departing from the spirit and scope of theinvention as claimed.

What I claim as my invention is:

1. A drafting instrument comprising a first plate and second platecomplementary thereto, said first plate having two sides of equal lengthand a substantially longer connected side, a

medial arcuate recess in said longer side, said second plate havingthree straight sides and a concave side, a transparent bearing bracketsuperimposed on said first plate and extending over said recess, acompanion transparent bearing bracket secured to said second plate andextending outwardly from the concave side, a pivot element connected tosaid brackets, a circular protractor mounted on said pivot element anddisposed in said concaved side and recessed side of the second and firstplates and in a common plane with said plates and means for releasablylocking said plates in adjusted interrelated positions around thecircumference of the protractor.

2. A drafting instrument comprising a first 4 plate and a second plateassociated therewith, said first plate having a base and a pair ofopposed sides of equal length connected to the opposite ends of saidbase, said sides being converged inwardly and joined at a common point,

said base having a medial arcuate recess, said second plate having amajor end constituting a base and a pair of equal sides joined at oneend to the opposite ends of the base and converging inwardly therefrom,a concave minor end connected to the opposite ends of the sides, atransparent bearing bracket secured to the upper surface of said firstplate and extending forwardly of the medial portion of the base, acompanion transparent bearing bracket fixed on the upper surface of saidsecond plate adjacent the medial portion of the base and extendingforwardly of the concave minor end, a pivot element conheated to theextended ends of said brackets, a circular transparent protractormounted at its center on the pivot element, said protractor beundersideof each of the plates, a diametrically reduced bore vertically disposedthrough said plates from the recess, a threaded locking pin seated insaid recesses and extended through the plates and the brackets adjacentthe protractor, a complementary internally threaded locking nut receivedon said pins.

WILLIAM H. HOWARD.

(CITED The following references are of record in the file of thispatent:

UNITED STATES PATENTS

